Vapor chamber-tank unit



Oct. 15, 1963 3,106,927

A. MADWED VAPOR CHAMBER-TANK UNIT F iled Jan. 15, 1962 s Sheets-Sheet 1INVENTOR. fl Z 66m! Mad weal 17 7' TOENEYS 0a. 15, 1963 A. MADWED3,106,9 7

VAPOR CHAMBER-TAM! UNIT Filed Jan. 15, 1962 1 3 Sheets-Sheet 2 INVENTOR.V Alfie/Z Mada/ed flTTUENEYS Oct. 15, 1963 A. MADWED VAPOR CHAMBER-TANKUNIT 3 Sheets-Sheet 5 Filed Jan. 15, 1962 Mad 95 Albert flTTORNEYSUnited States Patent 3,196,927 VAPOR CHAP/EER-TANK UNIT Aihert Madwed,261 River St, Bridgeport, Conn. Fiied .ian. 15, 1962, Ser. No. 166,22711 Chums. (Cl. lie -76) This invention relates to a novel unit for thetreatment of workpieces which are advanced therethrough on racks orhangers suspended from a conveying rail or the like. More specificallythe invention relates to a solvent treatment unit, such as a degreaseror dryer, adapted to be inserted at any desired position in line withother treatment tanks in a conventional conveyor-type plating apparatus.

Until the present it has been impossible or at least highly impracticalto dry or otherwise treat workpieces with highly volatile organicsolvents in a continuous conveyortype treatment apparatus such as anelectroplating apparatus of the type disclosed in US. Patents Nos.2,650,600 and 2,912,094. Such apparatus comprises a series of treatmenttanks or stations containing washing, rinsing and plating liquidsgenerally aligned in a row, and a conveying rail section over the row onwhich spaced workpiece carriers may be advanced by suitable pushermeans. The rail sections mounted on the frame of the apparatus may beraised and lowered to cause the workpieces to be immersed in andwithdrawn from the treating baths progressively.

The continuous conveyor-type plating apparatus has met with widespreadsuccess but does have serious disadvantages in that it requires that thetreating tanks be open at the top to provide access for the workpiecesand that the liquid in each tank be substantially at the same level.This has prohibited the use in such continuous conveyor apparatus ofvolatile organic treatment baths, highly advantageous for degreasing anddrying the workpieces because the volatile materials would escapethrough the open top of the tanks. The additional height of aconventional tank extending upwardly to provide a vapor chamber preventsits use on any conveyor-type plating apparatus since the height to whichthe workpiece carriers are raised is only sufiicient to clear thepartitions or walls separating the other tanks and is not nearlysufficient to clear the additional height required by a vapor chamber.To cause the carriers to be raised, this additional height would requirea rebuilding of the complete apparatus. This is costly andunsatisfactory since the additional height of the machine wouldmaterially interfere with its timing, would increase the amount of timerequired for the workpieces to be taken from one bath to the neXt andwould require much additional headroom for operation.

An object of the present invention is to provide a treatment tankadapted to contain volatile organic treating liquids and having asuperposed vapor chamber and adapted to be used on a conventionalconveyor-type treating apparatus in a safe and facile manner.

Another object of this invention is to provide a conveyor-type treatingapparatus having a vapor chambertank unit in combination with workpiececarriers which may be raised and lowered independently of the remainingworkpiece carriers on the apparatus.

Accordingly a feature of this invention is the provision of a treatmenttank which may be closed at the top and have in the sides of the vaporchamber aligned passages through which the work rack may travel to andfrom the vapor chamber, thereby avoiding the necessity of increasing thelift and fall of the Work beyond the normal range. The passages in theside of the vapor chamber are, according to the present inventioneifective- 1y closed, while the work is being treated, againstsubstantial escape of vapors from the chamber.

Other objects, features and advantages will be apparent in the light ofthe following description and accompanying drawings, in which:

FIGURE 1 is a side elevational view of a segment of a conveyor-typeplating machine containing a vapor chamber-tank unit according to thepresent invention, the conveyor chasssis being shown in the loweredposition.

FIG. 2 is a side elevational view corresponding to FEG. 1 but showingthe chassis in the raised position.

FIG. 3 is a side elevational View corresponding to FIG. 2 but showingthe workpiece carriers in transit being pushed along the conveyor railfrom one bath to the next.

FIG. 4 is a side elevational view of a segment of a conveyor-typeplating machine containing a vapor chamber-tank unit in combination witha rail segment and workpiece carriers which may be raised and loweredindependently of the remaining rail section of the apparatus, all of theworkpiece carriers being shown in the lowered position.

FIG. 5 is a side elevational view corresponding to FIG. 4 but showingthe rail section and workpiece carriers in the vapor chamber in theraised position.

PEG. 6 is a side elevational view corresponding to FIG. 4 but showingthe rail and workpiece carriers in raised position, the carriers beingpushed along and in transit from one bath to the next.

FIG. 7 is a side elevational view of a vapor chambertank unit accordingto the present invention and corresponding to the one shown in FIG. 2having the chassis in raised position and indicating by dotted lines thecorresponding position of the chassis when moved to the loweredposition.

FIG. 8 is a front elevational view on the line 22 of FIG. 7 showing thechassis in raised position and the vapor chamber doors in open position.

FIG. 9 is a front elevational view on the line 2--2 of FIG. 7 showingthe chassis in lowered position and the doors of the vapor chamber inclosed position.

FIG. 10 is a top plan view on the line 3-3 of FIG. 7 showing the vaporchamber doors in open position and illustrating the flow of air betweenthe inner and outer walls of the chamber creating an air curtain acrossthe work carrier passages.

In a conventional conveyor type plating apparatus of the type heretoforementioned, the workpieces are placed on the carrier at the introductoryend of the apparatus. The first carrier is pushed along the rail intoposition over the first tank or station containing for instance awashing solution, automatically lowered so as to immerse the workpiecesin the washing liquid, automatically raised after a preset time andpushed along the rail into position over the second tank or stationcontaining for instance a second washing solution. At the same time, asecond workpiece carrier, onto which other workpieces have been placed,is introduced onto the rail in spaced relationship to the first carrierand is pushed into position over the first tank or station.Simultaneously both carriers are lowered into the respective washingsolutions, raised after a preset time, and pushed along the rail intoposition over the next tank or station, while a new carrier withworkpieces is introduced onto the rail in spaced relationship to thesecond carrier for simultaneous treatment in the manner outlined.

Depending upon the number of treatment tanks or stations of theapparatus, a large number of workpiece carriers, each containing severalworkpieces, are simultaneously advanced, lowered, raised and againadvanced horizontally step-by-step from one station to the next. In thisway the workpieces are uniformly treated with washing, rinsing and otherbaths prior to plating and then uniformly treated in the plating bathsprior to their exit from the apparatus. Thus, while some of theworkpieces 3 are being immersed in washing baths, others aresimultaneously being immersed in rinsing baths, while others are beingimmersed in plating solution. Each workpiece is in turn immersed in thebath at each station for the same length of time as the precedingworkpieces.

FIGS. 1 to 3 illustrate a segment of a conveyor-type electroplatingapparatus having a series of suitable treating tanks 1 filled tosubstantially the same level with liquid washing, rinsing or platingcompositions, in combination with a vapor chamber-tank unit 2 having twotreating bath tanks 3 filled with volatile organic :degreasing or dryingsolvents to substantially the same level as the other tanks 1. All ofthe tanks are mounted on a suitable base support such as a concrete slabor floor, the vapor chamber-tank unit preferably being removablymounted.

To the base support are attached vertical chassis supports or columns 4.The chassis comprising the horizontal pusher bar 5 mounted forreciprocating movement and carrying pivoted pushers 6-, and the railsection 7 having removably and slidably attached thereto workpiececarriers 8, is mounted for vertical movement on the columns 4 bybracket-mounted rollers or the like (not shown). The pivoted pushers 6are adapted to advance the carrier 8 on forward movement and to pivot onreverse movement or back stroke to clear the next carrier 8 and fallinto position therebehind to advance the same on the next forwardstroke.

The vapor chamber-tank unit 2, as more clearly illustrated by FIGS. 7 to10, comprises an upper vapor condensing chamber 10 covered by a topsection 11, preferably removable, and having mounted on or in the sidewalls thereof condenser coils 12 containing coolant. On the front andrear walls of the vapor chamber are slidably mounted access and exitdoors 13 adapted to be opened and closed along tracks 14 by means ofhydraulic pistons 15 or the like in a direction perpendicular to thedirection of the chassis which is adapted to pass therethrough.

Thus, as may be seen :from the drawings, the vapor condensing chamber 10is closed on all sides except for an open bottom providing access to thelower tank section and except for the doors which may be opened toprovide passages through which the work carriers are adapted to travelinto and out of the vapor chamber.

The doors 13 are preferably constructed to provide horizontal air spacesor channels 16 therein and thus allow for the passage of airtherethrough. The door tracks 14 and the doors 13 are mounted within theinner and outer walls of the vapor chamber as may be more clearly seenfrom FIG. 10 which shows the inner walls 20' and the outer walls 21.Between the inner and outer walls is an air space 22 surrounding theentire circumference of the vapor chamber and having mounted therein afan 23 or other air irnpelling means for creating a strong flow of airaround the air space 22 sufiicient to create an air curtain 24 acrossthe entry and exit passages when the doors -13 are opened. Thissubstantially prevents the escape of any uncondensed vapors from thevapor chamber.

Around the entire inner circumference at the bottom of the inner wall ofthe vapor chamber is a gutter 25 for collecting the condensed solventvapors which liquefy along the inner wall and on the inner surface ofthe doors 13. The gutter is provided with a drainage pipe 26 leading toa separator 27 which extracts impurities such as water from the organicbath solution and return the latter to the desired receptacle or tank 3in the base of the unit by means of pipe 28. The separator may also beconnected by a drainage pipe to the door housings to remove vaporscondensed the hollow doors and in the air space 22 between the walls, ifdesired.

The entry and exit doors 13 on the front and back walls of the vaporchamber are caused to open and close automatically in timed relationshipwith the movement of the chassis and the transit of the workpiececarriers. The doors are only closed when the chassis is in the loweredposition and the workpiece carriers are immersed in the treating baths.The doors are automatically retracted when the chassis has been raisedto withdraw the workpiece carriers from the bath.

Upon leaving the bath, the remaining volatile degreasing or dryingsolvent evaporates from the workpieces and from the carrier, but it isprevented from escaping from the vapor chamber by the air curtains 24created by the swift current of air circulating within the air spaces 22and through the hollow air passages 16 in the doors.

Next the pushers 6 on the pusher rod 5 make contact with the slidablymounted carriers '8 on the rail section 7 and advance the carriers tothe next receptacle or tank as illustrated by FIG. 3. Each workpiececarrier is, in turn, advanced through the entry air curtain, immersed inbath A of the vapor chamber tank, retracted, immersed in bath B of thevapor chamber tank, retracted and advanced through the exit aircurtain'in perfectly dry condition, free of any water stains or thelike.

The vapor chamber doors are providedon their lower edges with cutawayportions 13a (FIG. 8) preferably having gaskets or bushings, so as toenvelop the pusher rod and rail and provide a seal when the doors areclosed so that the entire unit is relatively airtight. However, it issufficient in many instances to provide the cutaway portions on thedoors so that they close snugly around the rod and rail andsubstantially prevent the escape of vola tiles.

In the case of electroplating, current is applied to the conductive railsection 7 in known manner and passes through the conductive workpiececarriers 8 to the workpieces when the chassis is in the loweredposition.

The liquid bath tanks 1 and 3 may be provided with suitable heatingmeans such as a burner, hot plate or the like in base spaces In and 3a,if desired, to maintain the baths at a constant and elevatedtemperature.

In another embodiment of the present invention, as illustrated by FIGS.4 to 6 of the drawing, the workpiece carriers within the vapor chambermay be raised and lowered independently of the remaining carriers on theapparatus. The principal advantages of such embodimerit are that it isgenerally preferred to immerse the workpieces in the degreasing ordrying solvents in the tanks of the vapor chamber unit for shorterperiods of time and to withdraw them from the solvents at a slower ratethan is the case with the workpieces in the other washing, rinsing orplating tanks on the apparatus. In this way, the workpieces may beimmersed for a short time in the drying or degreasing solvent and slowlywithdrawn to allow the liquid solvent such as trichloroethylene to Howfrom the workpieces. Any residual solvent remaining on cracks andcrevices of the workpieces is evaporated in the vapor chamber,condensed, collected by the gutter 25, purified to separate the solventfrom water or the like, and returned to the solvent tank 3.

As shown by FIGS. 4 to 6, the independent vertical suspension of theworkpiece carriers 8 in the vapor chamber-tank unit is brought about byproviding the unit with a vertical column 4a in the center thereofhaving mounted for vertical movement thereon a rail section 7b adaptedto support two workpiece carriers, as illustrated, and positioned toalign in the raised position with rail sections 70 mounted in the upperfront and rear walls of the vapor chamber by mounts 7d. Rail sections 70are positioned to align with rail sections 7a on the chassis when thechassis is in raised position so as to form a continuous rail over whichthe workpiece carriers may be pushed for transit from one bath to thenext.

The vapor chamber-tank unit also has horizontally slidably mountedthereon pusher bar section 5b on mounts 5c, the bar section being sopositioned to align with pusher bar sections 5d when the latter arebrought to the raised position, to form a continuous pusher bar foradvancing the workpiece carriers as illustrated by FIG. 6.

The doors of the vapor chamber of FIGS. 4 to 6 are similar inconstruction and operation to the doors discussed hereinbefore andillustrated for instance by FIG. 8, with the exception that the cutawayportions 13a adapted to envelop the pusher bar and rail are located onthe upper edges of the doors, since the bar and rail sections at theentry and exit passages-of the chamber remain at the raised position asillustrated by FIG. 4. The rail sections 7c are supported by braces (notshown) so positioned as not to interfere with the transit of theworkpiece carriers over the rail. The pusher bar section 512 is slidablyattached to mounts 5a which support the bar without interfering with thelongitudinal reciprocation thereof or the movement of the pivotedpushers.

In view of the discontinuity of the rail sections supporting theworkpiece carriers, suitable means are used to conduct current to theworkpieces in the case of electroplating, as is obvious to those skilledin the art.

As mentioned hereinbefore, the vapor chamber-tank unit of the presentinvention may be inserted at any desired position on a conventionalconveyor-type plating apparatus or the like. This may be accomplished byremoving the top section 11 of the device to provide access to thechamber for the pusher bar and rail sections and then replacing the topsection, or by disassembling the pusher bar and rail sections and thenreassembling them within the chamber and through the door openings.

On a continuous electroplating apparatus the vapor unit 2 may bepositioned at or near the beginning or introductory end of the apparatusand the tank may contain suitable volatile degreasing liquid. Thesolvent in receptacle A, such as trichlorethylene or perchlorethylene,removes grease and grit from the workpieces. The workpieces then aremoved to receptacle B which contains the same solvent but in purer formfree from grease and grit. When the workpieces leave the vapor chamberunit, they are completely clean and free from grease and grit.

The vapor unit may also be positioned at the end of the apparatus fordrying the plated or otherwise treated workpieces before they leave theapparatus. For this purpose the liquid in the vapor chamber tank may betrichlorethylene or perchlorethylene in which case the workpieces mustfirst be immersed in a water-displacing oil. The oily workpieces arethen brought into the vapor unit whereby they are cleaned of oil anddried. The waterdisplacing oil treatment may be dispensed with if theliquid in the vapor chamber tank is a drying liquid such as a modifiedtrichlorethylene available under the name Trisec.

After the drying treatment in the vapor unit, the workpieces arecompletely clean and dry even in the cracks and crevices or recesses ofintricately shaped workpieces. This is in sharp contrast to conventionaldrying methods using ovens, sawdust, centrifuges, hot and cold blastdryers and the like, which require that the workpieces be removed fromthe conveyor apparatus and which leave the workpieces with water stains,particularly in the case of intricately shaped parts.

The blower means illustrated for instance in FIG. of the drawings as amotor-operated fan 23 is in operative communication with the spacebetween the inner and outer walls of the vapor chamber and may be varieddepending upon the size of the unit and the efficiency of the aircurtain desired. Also the blower may be mounted outside the unitprovided that the blower remains in operative communication with thespace between the inner and outer walls and the air current therefrom ischanneled into the air space 22 to provide the desired result. In mostcases the blower is in continuous operation to provide a continuous aircurtain even when the doors are in closed position, particularly whenthe swiftness of optroplating apparatus, it should be understood thatthe present vapor chamber device may be advantageously used as anintegral part of any conveying apparatus whether it be used for plating,bright pickling, blackening, phosphating, or the like.

It should also be understood that the vapor chambertank unit of thepresent invention has been described spe cifically to correspond withthe accompanying drawings but that many variations will be obvious tothose skilled in the art in the light of the foregoing description. Forinstance it is not necessary that the chamber doors be wide and hollowas illustrated. Thin doors may be mounted against the inner or outerwall of the vapor chamber so that the air curtain need not pass throughthe doors. Also, other suitable power-operated door-actuating means maybe used in place of the pistons illustrated.

Although the dual receptacle tank section of the present unit, asillustrated, is the preferred form of the present invention, there is nocriticality in the number of receptacles, and the end use will in mostcases determine whether one or more receptacles are required.

Various other modifications and alterations in the construction of thepresent vapor chamber device may be made without departing from thescope of the present invention as indicated by the appended claims.

I claim:

1. In work treating apparatus having means for conveying work carriershorizontally step-by-step from one station to another and means formoving the work carriers vertically at at least some of said workstations, one of said stations having a tank section open at the topadapted to contain an amount of volatile liquid material into which thework carriers may be submerged by said means for moving the samevertically, and a vapor collecting chamber section above said tanksection and open at the bottom into which the work carriers may beraised from the volatile liquid material in the tank section by saidmeans for moving the carriers vertically, means in said vapor chamber tocondense said liquid material when volatilized, said vapor chamber beingclosed on all sides except for said open bottom and work carrierpassages on two oppositely positioned walls of said chamber, doorsadapted to close and open said passages, said doors in open positionbeing adapted to permit entry of said work carriers on said conveyingapparatus to said vapor chamber and said doors having openings toreceive said conveyor means when in closed position, and means in thevapor chamber section for substantially preventing the escape of saidvolatilized liquid material from said vapor chamber when the doorsthereof are in the open position.

2. Work treating apparatus as defined in claim 1 in which said vaporchamber section has spaced inner and outer walls and said doors slide insaid space between said inner and outer walls between open and closedpositions.

3. Work treating apparatus as defined in claim 1 in which said vaporchamber section has spaced inner and outer walls and means forsubstantially preventing the escape of said volatilized materialcomprising a blower in operative communication with the space betweensaid inner and outer walls, said inner and outer walls of the vaporchamber section directing an air curtain from said blower across saidwork carrier passages when the doors are in the open position.

4. Work treating apparatus as defined in claim 1 in which there arepower-operated means for opening said doors to permit entry of said workcarriers on said conveying apparatus and for closing said doors afterentry of said work carriers.

5. In work treating apparatus having means for conveying Work carriershorizontally step-by-step from one station to another and means formoving the work car riers vertically at at least some of said workstations, one of said stations having a tank section open at the topadapted to contain an amount of volatile liquid ma- 9 terial into whichthe work carriers may be submerged by said means for moving the samevertically, and a vapor collecting chamber section above said tanksection and open at the bottom into which the work carriers may beraised from the volatile liquid material in the tank section by saidmeans for moving the carriers vertically, means in said vapor chamber tocondense said liquid material when volatilized, said vapor chambersection having spaced inner and outer walls and being closed on allsides except for said open bottom and work carrier passages on twooppositely positioned walls which form a portion of said spaced innerand outer walls of said chamber, and means in the vapor chamber sectionbetween said spaced inner and outer walls for providing an air curtainacross said passages for substantially preventing the escape of saidvolatilized liquid material from said vapor chamber.

6. Work treating apparatus as defined in claim 1 in which said vaporchamber section has spaced inner and outer walls, work carrier passageson two oppositely positioned inner and outer walls of said chamber, andsaid doors slide in said space between said inner and outer walls,between open and closed positions, said doors having spaced inner andouter panels and open edges and the means for substantially preventingescape of volatilized material comprises a blower in operativecommunication with the space between said inner and outer walls, saidinner and outer walls of the vapor chamber section and the inner andouter panels of the doors directing an air curtain from said blowerpassing through said open edges horizontally across said passages whenthe doors are in the open position.

7. A vapor unit having a tank section open at the top and adapted tocontain an amount of volatile liquid material into which workpieces tobe treated may be immersed and a vapor collecting chamber section abovesaid tank section and open at the bottom into which workpieces to bedried are adapted to be raised from said volatile liquid material insaid tank section, means in said vapor chamber to condense said liquidmaterial when volatilized, said vapor chamber section having spacedinner and outer Walls and being closed on all sides except for said openbottom and work carrier passages on two oppositely positioned Wallswhich form a portion of said spaced inner and outer walls of saidchamber, and means in the vapor chamber section between said spacedinner and outer walls for providing an air curtain across said passagesfor substantially preventing the escape of said volatilized liquidmaterial from said vapor chamber.

8. A unit having a tank section open at the top and adapted to containan amount of volatile liquid material into which workpieces to betreated may be immersed and a vapor collecting chamber section abovesaid tank section and open at the bottom into which workpieces to bedried are adapted to be raised from said volatile liquid material insaid tank section, means in said vapor chamber to condense said liquidmaterial when volatilized, said vapor chamber being closed on all sidesexcept for said open bottom and work carrier passages on two oppositelypositioned walls of said chamber, doors adapted to close and open saidpassages, said doors in open position being adapted to permit entry ofwork carriers to said vapor chamber and said doors in the closedposition being adapted to substantially prevent the escape of saidvolatilized liquid material, power-operated means for opening said doorsto permit entry of said work carriers to said vapor chamber and forclosing said doors after entry of said work carriers, and means in thevapor chamber section for substantially preventing the escape of saidvolatilized liquid material from said vaporchamher when the doorsthereof are in the open position.

9. A unit as defined in claim 8 in which said vapor chamber section hasspaced inner and outer walls, and said two oppositely positioned wallsform a portion of said spaced inner and outer walls, and said doorsslide in said space between said inner and outer walls between open andclosed positions.

10. A unit as defined in claim 8 in which said vapor chamber section hasspaced inner and outer walls, and said two oppositely positioned wallsform a portion of said spaced inner and outer walls, and means forsubstantially preventing escape of said volatilized material comprisinga blower in operative communication with the space between said innerand outer walls, said inner and outer walls of the vapor chamber sectiondirecting an air curtain from said blower across said work carrierpassages when the doors are in the open position.

11. A unit as defined in claim 8 in which said vapor chamber section hasspaced inner and outer walls, work carrier passages on two oppositelypositioned walls which form a portion of said spaced inner and outerwalls of said chamber, and said doors slide in said space between saidinner and outer walls between open and closed positions, said doorshaving spaced inner and outer panels and open edges, and the means forsubstantially preventing escape of volatilized material comprises ablower in operative communication with the space between said inner andouter walls, said inner and outer walls of the vapor chamber section andinner and outer panels of the doors directing an air curtain from saidblower passing through said open edges horizontally across said passages when the doors are in the open position.

References Cited in the file of this patent UNITED STATES PATENTS RandFeb. 6, 1962

1. IN WORK TREATING APPARATUS HAVING MEANS FOR CONVEYING WORK CARRIERSHORIZONTALLY STEP-BY-STEP FROM ONE STATION TO ANOTHER AND MEANS FORMOVING THE WORK CARRIERS VERTICALLY AT AT LEAST SOME OF SAID WORKSTATIONS, ONE OF SAID STATIONS HAVING A TANK SECTION OPEN AT THE TOPADAPATED TO CONTAIN AN AMOUNT OF VOLATILE LIQUID MATERIAL INTO WHICH THEWORK CARRIERS MAY BE SUBMERGED BY SAID MEANS FOR MOVING THE SAMEVERTICALLY, AND A VAPOR COLLECTING CHAMBER SECTION ABOVE SAID TANKSECTION AND OPEN AT THE BOTTOM INTO WHICH THE WORK CARRIERS MAY BERAISED FROM THE VOLATILE LIQUID MATERIAL IN THE TANK SECTION BY SAIDMEANS FOR MOVING THE CARRIERS VERTICALLY, MEANS IN SAID VAPOR CHAMBER TOCONDENSE SAID LIQUID MATERIAL WHEN VOLATILIZED, SAID VAPOR CHAMBER BEINGCLOSED ON ALL SIDES EXCEPT FOR SAID OPEN BOTTOM AND WORK CARRIER PASSAGEON TWO OPPOSITELY POSITION WALLS OF SAID CHAMBER, DOORS ADAPTED TO CLOSEAND OPEN SAID PASSAGES, SAID DOORS IN OPEN POSITION BEING ADAPTED OPERMIT ENTRY OF SAID WORK CARRIERS ON SAID CONVEY APPARATUS TO SAIDVAPOR CHAMBER AND SAID DOORS HAVING OPENINGS TO RECEIVE SAID CONVEYORMEANS WHEN IN CLOSED POSITION, AND MEANS IN THE VAPOR CHAMBER SECTION OFSUBSTANTIALLY PREVENTING THE ESCAPE OF SAID VOLATILIZED LIQUID MATERIALFROM SAID VAPOR CHAMBER WHEN THE DOORS THEREOF ARE IN THE OPEN POSITION.